Radium-223 chloride impact on skeletal-related events in patients with castration-resistant prostate cancer (CRPC) with bone metastases: A phase III randomized trial (ALSYMPCA).

Abstract

9 Background: Radium-223 chloride (Ra-223) is a 1st-in-class alpha-pharmaceutical targeting bone metastases (mets) with high-energy alpha-particles of short range (<100 μm). ALSYMPCA, a phase III, double-blind, randomized, multinational study, compared Ra-223 plus best standard of care (BSC) vs placebo (pbo) plus BSC in patients (pts) with bone mets in CRPC. The primary endpoint was OS; secondary endpoints included skeletal-related events (SREs). Methods: Eligible pts had progressive, symptomatic CRPC with ≥ 2 bone mets on scintigraphy and no known visceral mets; were receiving BSC; and either previously received docetaxel, were docetaxel ineligible, or refused docetaxel. Pts were randomized 2:1 to receive 6 injections of Ra‐223 (50 kBq/kg IV) q4 wks or matching pbo and stratified by prior docetaxel use, baseline alkaline phosphatase level, and current bisphosphonate use. Results: 922 pts (Ra-223, n = 615; pbo, n = 307) were randomized from 6/2008-2/2011. Based on data from a planned interim analysis (n = 809), unblinded June 2011, Ra-223 significantly improved OS in pts with CRPC with bone mets vs pbo (median OS 14.0 vs 11.2 mo, respectively; two-sided P = 0.00185; HR = 0.695; 95% CI, 0.552-0.875). SREs were lower in the Ra-223 vs pbo group, and time to 1st SRE was significantly delayed (median time to SRE 13.6 mo vs 8.4 mo, respectively; P = .00046; HR = .610; 95% CI, .461-.807). Conclusions: Ra-223 significantly delayed time to 1st SRE and SRE components, except surgical intervention. These reductions in SREs, particularly SCC, are noteworthy. Ra-223 is an effective therapy with a highly favorable safety profile and may provide a new standard of care for treatment of CRPC pts with bone mets. [Table: see text]